I stepped on a nail at a backyard barbecue. It wasn’t rusty. Do I need a tetanus shot?

If it has been more than 10 years since your last tetanus booster, the answer is yes—whether or not the nail was rusty. Tetanus is caused by Clostridium tetani, a type of bacterium commonly found in soil and animal feces that can enter the bloodstream through a cut or puncture wound. The bacteria produce toxins that interfere with the central nervous system, resulting in painful muscle rigidity, spasms and lockjaw. Tetanus is serious—about 11 percent of cases are fatal—but it’s treatable and preventable with the combined tetanus, diphtheria and pertussis (Tdap) vaccine. Play it safe and check with your doc to see if you’re due. And be sure to keep your wound clean to avoid other infections.